H. Fukuda

APPLICATION OF PIXE ANALYSIS TO THE STUDY OF ELECTROKINETIC REMOVAL OF CESIUM FROM SOIL

Thick-target PIXE analysis was applied to the study of electrokinetic soil remediation technique. In order to simulate radioactive soil contamination by 137Cs, salt of stable cesium was mixed with soil samples. These soil samples were subjected to electrolysis for up to 36 hours with a field gradient of ≈ 1-3 V/cm. After the electrolysis, we measured the distribution of Cs concentration in the soil along the electrolysis cell by PIXE analysis. LX-rays of cesium were used for the analysis. The Cs concentrations in the drain water sampled from the cathode well were also evaluated. After the electrolysis the migration of cesium from the anode to the cathode was clearly observed. Water supply into the anode well enhanced the removal rate. We found that the main driving force of the migration of Cs+ observed in this work was not electrophoretic migration, but electroosmotic flow in the soil samples. Owing to the spectral interference by major metallic elements in the soil, the minimum detectable concentration of cesium by the present method was limited to ≈ 800 ppm.

Experimental and numerical study of dose distribution around a syringe needle-type proton-induced X-ray source for radiotherapy

A syringe needle-type proton-induced monochromatic X-ray source was proposed to solve the issue that could occur in practical brachytherapy, such as loss of seed sources and radiation exposure to surgical staff. This paper discusses comparison between experimental results and a Monte Carlo numerical simulation of the dose distribution around the needle. Some simulation results for different source designs are presented as a first step of the design optimization.

Production of quasimonochromatic X-ray microbeams using MeV-protons and a polycapillary X-ray half lens

In this paper, we have proposed monochromatic X-ray microbeams, produced by a proton-induced X-ray technique and a polycapillary X-ray half lens, as a tool for micro-X-ray fluorescence (XRF) analysis. A 30 μm thick planar Cu target was irradiated by a 2.5 MeV proton beam to produce Cu Kα X-rays (8.0 keV), and a polycapillary X-ray half lens was utilized to focus the X-rays emitted behind the Cu target. The focal spot size of the focused X-ray beam was 250 μm at full width at half maximum, which was verified using a knife-edge scanning method. The output focal distance and the depth of focus of the optics were measured to be 47 mm and 1 mm, respectively. A square grid pattern of Co thin films, formed on a thick Cu substrate by thermal evaporation, was used as a test sample for evaluation of the analytical performance of the micro-XRF setup. Two-dimensional mapping of the Co distribution on the Cu substrate was successful, and the spatial resolution was consistent with the beam spot size. For this Co layer, a minimum detection limit of 2.3 ng was achieved.

DEVELOPMENT OF A TARGET POSITIONING SYSTEM BASED ON A LASER POSITION SENSOR FOR HIGH-EFFICIENCY WAVELENGTH-DISPERSIVE PIXE ANALYSIS

A precise target positioning system based on a laser position sensor was developed for a high-efficiency wavelength dispersive PIXE analysis. The absolute position and the target surface profile were clearly observed using this position sensor, which was rigidly connected to the target vacuum chamber. By using a thin proton beam (width = 2 mm) and a small target (width = 1 mm), the optimum target position for the measurement of chlorine (Cl) Kβ X-ray could be determined from X-ray detection yields measured at various target positions. We found that the relationship between the X-ray detection yield and the target position can be explained by the target size as well as the incident proton beam width. After precise adjustment of the target position using the above system, target samples with two different Cl compounds, NaCl and NH4Cl, were successfully distinguished from the difference in the measured profiles of Kβ X-ray spectra.

APPLICATION OF ION EXCHANGE PAPER TO PRECONCENTRATION OF CHROMIUM (III) AND CHROMIUM (VI) IN WATER FOR PIXE ANALYSIS

The most important species of chromium (VI) formed in water are anions such as CrO42-, whereas chromium (III) is mainly present in the form of cationic species such as Cr(OH)2+. Pure water and tap water samples were artificially contaminated with mixture of chromium (VI) and chromium (III) standard solutions. Sequential filtration through commercially available Whatman P81 cellulose phosphate paper and Whatman DE81 DEAE cellulose paper was employed for separation and preconcentration of chromium (III) and chromium (VI) in these water samples, respectively. The PIXE measurements of these filter paper samples were performed using 2-MeV proton beams delivered by a tandem pelletron accelerator at Research Laboratory for Nuclear Reactors, Tokyo Tech. The beam current and the measuring time for each sample were 1 nA and 10 minutes, respectively. Instrumental detection limits were 60 ng for chromium (VI) and 120 ng for chromium (III). Detectable range for chromium (VI) and chromium (III) in water were ≧ 10 ppb and ≧ 50 ppb, respectively. For chromium (VI), the detectable range was considerably lower than the maximum allowed concentration of 50 ppb for chromium (VI) in both the drinking water standards and the environmental quality standards in many countries.

Construction of 1.7 MV Pelletron Tandem Accelerator System and Its Application to Human Resource Development at Tokyo City University Atomic Energy Research Laboratory

Naoto HAGURA, Noriyosu HAYASHIZAKI, Takafumi UCHIYAMA, Yoshiyuki OGURI, Hitoshi FUKUDA, Katsunori KAWASAKI, Tamotsu TORIYAMA, Koichi MOCHIKI, Yukiko OKADA, Jun KAWARABAYASHI, Ishi MITSUHASHI and Haruaki MATSUURA 1 Department of Nuclear Safety Engineering, Tokyo City University, 1-28-1 Tamazutsumi, Setagaya-ku, Tokyo 158-8557, Japan 2 Atomic Energy Research Laboratory, Tokyo City University, 971 Ozenji, Asao-ku, Kawasaki, 215-0013, Japan 3 Laboratory for Advanced Nuclear Energy, Institute of Innovative Research, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan 4 Technical Department, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan 5 Electrostatic Accelerator Research Laboratory, 3-1-22-P2-502 Honcho, Higashikurume-city, Tokyo 203-0053, Japan 6 Laboratory for Materials Engineering with Quantum Beams, 4-2-17 Nishigahara, Kita-ku, Tokyo 114-0024, Japan

Direct observation of dose distribution around a syringe-needle type proton-induced X-ray source using liquid scintillator and a CCD camera

This paper discusses a method to directly observe the dose distribution around a syringe-needle-type proton-induced monochromatic X-ray source proposed to avoid the risk that could exist in conventional brachytherapy. Images taken by using liquid scintillator and a high sensitivity CCD camera are presented and the dose distribution is qualitatively evaluated by comparing it with a Geant4 Monte Carlo simulation result.

Selective internal radiotherapy using proton-induced monochromatic X-rays and cancer-targeting nanoparticle sensitizers

In this paper, we propose a highly-selective radiotherapy based on monochromatic X-rays and cancer-targeting gold nanoparticle (GNP) sensitizer. In order to deliver the low-energy monochromatic X-rays which selectively ionize the Au L-shell into the cancerous tissue deep inside the patient’s body, we employ a syringe-needle type X-ray source driven by an MeV proton beam. From a simple numerical evaluation, we found that optimization of the primary X-ray energy was essential to enhance the dose around the nanoparticle. In order to confirm the above idea qualitatively, we performed a simulation experiment in the atmosphere, where 100 nm Au foils were used instead of the GNPs. The experimental result showed that the dose around the Au foils was much higher than that at positions away from the foils, owing to short-range secondary electrons from the foils.

Digital subtraction cineangiography using proton-induced quasi-monochromatic pulsed X-rays

Two different kinds of metallic plates on a rotating disk target were irradiated with a MeV proton beam, and quasi-monochromatic pulsed X-rays with different energies around the absorption edge of the contrast medium were alternately produced. By using these dual-energy X-rays and a high-sensitivity X-ray movie camera, we took a motion picture of the transmission image of a periodically moving phantom, which simulated a rat heart as a test animal. We found that the enhanced movie imaging of the contrast agent is available by subtraction between adjacent picture frames.

CHEMICAL SPECIATION OF CHLORINE PRESENT IN PARTICULATE COMBUSTION PRODUCTS OF ORGANIC CHLORINE COMPOUNDS BY EMPLOYING HIGH-RESOLUTION PIXE ANALYSIS

The chemical speciation of chlorine (Cl) in particulate matter samples produced by the laboratory burning of organic Cl compounds was tested by employing the high-resolution measurement of Kβ X-rays based on a wavelength-dispersive proton-induced X-ray emission (WD-PIXE) technique. Targets for proton irradiation were prepared by depositing particulate burning products on aluminum foils placed on a simple barrel burner. Standard inorganic (NaCl, MgCl2, CaCl2, NH4Cl, and AlCl3) and organic (polyvinyl chloride and polyvinylidene chloride) Cl compounds were prepared for spectral comparison. We found that the Cl-Kβ1 peak energies for these organic compounds are higher by approximately 1 eV than those for inorganic compounds. For burning products of these organic compounds, the peak energies were found to be located between those for organic and inorganic compounds. This result indicates that the organic Cl compounds were decomposed to smaller molecules during the burning process but these fragments still existed in the organic form.